Match List-I with Match List-II
List-I (Metal)               List-II (Application)
(A) Cs                    (I)    High temperature thermometer
(B) Ga                   (II)   Water repellent sprays
(C) B                     (III)  Photoelectric cells
(D) Si                    (V)   Bullet proof vest
Choose the most appropriate answer from the options given below

We need to match each metal with its correct application. Caesium (Cs), an alkali metal with a very low ionization energy, is highly sensitive to light and is therefore used in photoelectric cells. Thus (A) Cs $$\rightarrow$$ (III) Photoelectric cells. Gallium (Ga) features a low melting point (29.76°C) and a high boiling point (2204°C), providing a wide liquid range that makes it ideal for high temperature thermometers. Hence (B) Ga $$\rightarrow$$ (I) High temperature thermometer.

Boron (B) forms extremely strong and lightweight fibres, which are utilized in bullet proof vests (body armour). This corresponds to (C) B $$\rightarrow$$ (IV) Bullet proof vest. Silicon (Si) gives rise to silicones (organosilicon polymers) that are hydrophobic and thus employed in water repellent sprays. Consequently, (D) Si $$\rightarrow$$ (II) Water repellent sprays.

The final matching is (A) - (III), (B) - (I), (C) - (IV), (D) - (II), so the correct answer is Option A.